This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This protocol hypothesizes that 6 months of fiber supplementation will improve ovulation in women with PCOS by improving insulin sensitivity independent of weight loss. In this pilot study, we will determine the feasibility of conducting a larger double-blind, randomized trial in women with PCOS to test this hypothesis. Therefore, we will evaluate 15 women with PCOS between ages 18 to 45 years (body mass index ? 45 kg/m2) over 10 months, starting with a 4-month intervention-free observation period to establish baseline ovulatory rate, followed by a 6-month intervention period to determine the effect on ovulation of adding up to 22 g/day of fiber supplementation to their usual weight-maintenance diets (to achieve 28-36 g fiber/day assuming baseline dietary intake of 6-14 g fiber/day). Fiber supplementation, as opposed to change in dietary fiber intake, could feasibly be translated into clinical practice. The Specific Aims: a) Generate preliminary data on the range of outcome measures at baseline and after 6 months of fiber supplementation in terms of: 1) ovulation rates, as measured by urinary pregnanediol-3-glucuronide measurements;2) insulin sensitivity, as measured by frequently sampled intravenous glucose tolerance testing (FSIVGTT);3) concentrations of circulating androgens, estradiol, sex-hormone binding globulin, and luteinizing hormone;and 4) satiety, as measured by a visual analog scale. b) Quantify enrollment strategies, retention, compliance, participant characteristics, and data collection challenges. c) Determine whether a dose of up to 22 grams of liquid fiber supplementation would be tolerable and sufficient to affect ovulation rates and insulin sensitivity in women with PCOS. D) Determine whether 6-month duration of fiber supplementation is sufficient to affect to affect ovulation rates and insulin sensitivity in women with PCOS.